The invention generally relates to wrist-worn cardiac monitors. More particularly, the invention concerns a wrist-worn ECG monitor having integral electrodes for recording and teletransmitting ECG data to a remote site for analysis by a diagnostician.
Known wrist-worn cardiac monitors are extremely limited in functionality. For example, some conventional monitors simply monitor and display pulse rate and thus provide no ECG data recording capability at all. Others record ECG data and provide only for the local playback of recorded data and thus provide no remote diagnostic capability. Still others require external electrodes on the ends of a cable for detection of an ECG signal near the heart of the cardiac patient--often necessitating the use of messy conductive gels--and thus are difficult to hook up and use, especially for long-term monitoring of a relatively active patient. Problems abound in producing small, lightweight ECG monitors that provide for long-term cardiac event recording and remote professional diagnostic and prescriptive patient care.
Accordingly, it is a principal object of the present invention to provide a self-contained, wrist-worn ECG monitor that provides at least single event recording and telecommunication of ECG data to a remote site for professional diagnosis.
It is another important object of the invention to provide such a monitor with the greatest possible functionality in an extremely compact, integral housing.
Yet another object is to provide such a monitor that reliably detects and records ECG signals without the use of external electrodes or messy gels or other skin preparation.
It is also an object of the invention to provide an improved dry skin electrode system that is an integral part of the housing of such a monitor.
Another object is to render such a wrist-worn monitor that easily and conveniently can be used by a cardiac patient without assistance by another, for long-term ambulatory patient care.
Still another object is to make such a wrist-worn ECG monitor the multiple functions of which readily can be operated with the patient's other hand.
One equally important object is to provide such functionality in a lightweight, compact, wrist-worn monitor that yet has the capacity to record multiple events that may occur over a long period of time, e.g. days.
One other object of the invention is to make such a monitor easily manufactured and maintained, and cost effective.
Briefly summarizing the invention in its preferred embodiment, a wrist-worn monitor is provided that, without external connections of any kind, enables local, multiple event ECG data recording and telecommunication to a remote site, as well as providing the time and date functions normally provided by a wristwatch. The monitor is housed in an extremely compact and lightweight housing and is operable by the patient's simply placing the other palm over a portion of the monitor's face to contact an upper skin electrode. Custom very-large-scale integrated (VLSI) circuit components contained within the housing include ECG signal and abnormal event detection circuitry, analog-to-digital (AD) and digital-to-analog (DA) conversion circuitry, memory and processor circuitry for scanning the pushbuttons and displaying selected chronometric, cardiac and status information. Circuitry is also provided to drive an integral speaker for the telecommunication of ECG signal or cardiac event data via telephone lines to a remote site for so-called "over-read", diagnosis and archival recording.
The monitor's housing includes dual, integral dry skin electrodes located on a wrist-contacting, inner or rear base plate and on an outer or front surface contactable by the palm of the patient's other hand. The electrodes preferably are formed by plating a region of a stainless steel or other base metal expanse with a thin layer of titanium nitride (TiN), titanium carbide (TiC) or titanium carbo-nitride (TiCN). The microprocessor and associated electronics, including firmware executed thereby, employs a digital bandpass filter reliably to detect ECG signals characterized by QRS complexes or pacer and defibrillator pulses but t ignore noise and motion artifacts. A current draw measuring method implemented by the microprocessor and associated electronics monitors usage and predicts the end of life of the integral battery beyond which monitoring is halted, thereby to maximize long-term monitoring capacity, to avoid potentially inaccurate ECG data recording and to inform the patient when the battery should be replaced.
These and other objects and advantages of the invention will be more clearly understood from a consideration of the accompanying drawings and the following description of the preferred embodiment.